1. Field of the Invention
The present invention relates generally to an apparatus and method for non-invasively measuring aortic blood flow in a patient. More particularly, the invention relates to an apparatus and method for determining aortic blood flow by measuring the pressure differential between the left and right subclavian arteries.
2. Description of the Related Art
In a conventional flow apparatus and method, aortic blood flow is measured by one of several techniques that involve injection of a "bolus" of foreign material into the ventricle of the heart or into the aorta. The movement of the "bolus" is then monitored by thermal or nuclear (x-ray, gamma ray) sensors. All of these techniques have the severe disadvantage of being invasive. The foreign material injected is usually harmless, but some patients may have adverse reactions to it. These procedures usually must be performed in a "cath lab", which is a relatively expensive facility. This, in addition to the need for the services of a skilled cardiologist, make these procedures relatively expensive.
An alternative conventional apparatus and method uses ultrasonic imaging techniques to measure the blood flow velocity profile in the aorta. Total volumetric blood flow can be found by integration of the velocity profile. However, this method is very sensitive to movement artifacts. The equipment is also too large and sensitive to movements to be used on an ambulatory patient, or during surgery. The equipment is also relatively expensive.